The cliché claims that, in springtime, a young person’s fancy turns to love.
That is, unless they’re gearhead—in which case that attention is more likely focused on busting their car out of the garage and getting it out on the road.
But that’s often when they discover the vehicle’s battery is dead and, even after a quick jumpstart, the battery doesn’t always come back to life.
This calls for a little battery and starter circuit research and maintenance.
Car and truck batteries can be fickle devices—fair-weather friends who are only willing to help when the conditions are perfect.
Also like good friends, they need you to maintain a solid connection. This story is all about how to maintain a rapport with your battery and the starting and charging systems. The bottom line is if you maintain these systems now, they will take care of you when you need them.
Take a moment to read the attached Definitions section at the bottom of this article, as we’ll be using these terms throughout this story.
Understanding How Vehicle Batteries Work
First let’s cover a little bit of how batteries work.
Batteries are like people, they don’t perform as well in extremes of cold or hot weather. Much like humans, an automotive battery will perform at its best around 80 degrees F. but when the temperature drops to below freezing or surges in excess of 100 degrees F, batteries lose some of their efficiency.
This story will mainly address flooded lead-acid and AGM batteries as they are the most popular. There are now lithium-ion automotive batteries on the market and while powerful and lightweight, they cost a bit more and require their own specific battery chargers.
In any kind of weather, it takes voltage to push and amperage to crank over the starter motor. Car batteries are rated in cold cranking amps (CCA) to indicate how much amperage is available. For big cubic inch engines with high compression, this CCA also works as an indicator as to the power available to crank the engine. This, of course, assumes that the starting system is in good condition. We’ll cover some ways that enthusiasts can easily test both their battery and the starting and charging circuit to ensure that all these systems are up to the task.
The Impact of Seasonal Storage on a Car Battery
Springtime is a great time to initiate this project since the battery has probably been sitting unattended for several months. As an example, we tested the basic lead-acid battery in our ‘65 small-block-powered El Camino that had been unattended all winter in a non-heated garage. The battery tested at 12.25 volts using a typical digital multimeter. Based on our battery voltage chart, you can see that this means our battery was only slightly better than 60 percent charged. This is usually enough to start the car, but we decided to give the battery a nice, slow, low-amperage charge to bring it back up to a full state of charge.
This is a great place to explain how a simple test of open circuit voltage with a voltmeter will tell you quite a bit about battery condition. If a multimeter test displays less than 11 volts, this would indicate that this battery is greatly discharged and may be sulfated. This is a condition where lead sulfate crystals have formed on the active portion of the lead plates and interfere with the chemical process of creating voltage. If these crystals are allowed to grow and harden, this damages the plates and will eventually lead to high internal resistance and a dead battery.
Sulfation occurs when a battery sits unused for long periods of time at low voltage. There are two types of sulfation: soft and hard.
Soft sulfation is generally recently caused and is easier to remove through a specific process employed by the new generation of battery chargers that can break-up this soft sulfation and actually improve the condition of a battery. Hard sulfation is more difficult to remove and leads to eventual battery failure. The common indicator that a battery has suffered sulfation damage is that after charging, it will quickly lose voltage over a short period of time—often just a few hours.
Testing & Assessing a Vehicle Battery
Each cell in a 12 volt automotive starting battery should produce roughly 2.1 volts per cell and with six cells connected in series a fully charged car battery will produce around 12.6 volts. In the case of the battery we tested at 12.2 volts, this indicated it was at roughly 60 percent charge. With a simple recharge from our Schumacher battery charger set at a low 3 amps brought the battery back up to a full charge reading of 12.6 volts in a couple of hours.
After two days, the battery was still at 12.6 volts indicating that it was capable of holding a charge and was not damaged. However, if after several days the voltage had dropped back to 12.2 volts or lower with it merely sitting on the bench, this would indicate a damaged cell that would probably require replacing the battery.
Summit Racing carries several different battery testers that will help with this evaluation. These testers will add a 10 to 15 second load to the battery and then report with a voltage reading. Digital versions use a process to evaluate the battery’s internal resistance and offer a condition report based on this evaluation. A higher voltage reading after the test indicates a healthy battery. Another option is to take your battery to a local auto parts store that will test your battery for you for no cost.
This is a great place to dispel the urban myth about batteries discharging on a concrete floor. If a battery is left unattended for a long period of time, it will slowly discharge—but not because of its proximity to concrete.
If the battery top is dirty, try this simple test. Place two voltmeter probes at opposite ends of the top of the dirty battery but not connected to either terminal. Most often your voltmeter will offer a reading in millivolts (0.001 volt). This indicates a current flow discharge across the top of the battery.
Clean the battery and this voltage will be dramatically reduced. This is one reason why automotive batteries discharge even completely disconnected from the vehicle. Of course, even clean batteries eventually self-discharge, especially in severe cold or hot weather. Using a trickle charger is a great way to maintain the battery voltage and extend its life by maintaining its full charge voltage which also minimizes sulfation.
Testing & Assessing a Vehicle’s Charging System
Now that we have a handle on basic battery maintenance, we can move on to testing the starting and charging system. Hard starting problems are often blamed on the battery when the real culprits require more careful examination. Let’s start with the simplest of things by ensuring the battery terminals, posts, and connectors are clean and free of corrosion. We’ve seen examples of dark film on the terminals that doesn’t appear as corrosion but is sufficient to cause resistance and reduce current flow. While it may seem obvious, ensuring the battery connections are free of these simplest forms of corrosion can make a big difference.
One quick test of battery condition is to disable the ignition and monitor battery voltage during cranking. A healthy battery with a 12.4 or higher open circuit voltage should display a loaded voltage during cranking of roughly 11 to 11.5 volts. If the voltage drops much more than 2.0 volts (down to 10.5 for example), this indicates the battery is struggling.
Another evaluation of battery condition is to test open circuit voltage after this cranking test. Let’s say the voltage before the test is 12.4 but after 5 seconds of engine cranking the open circuit voltage falls to 12.1 volts and continues to drop, this is a clue that the battery is suspect. If the voltage is stable after the load test, then the battery is probably in good condition.
Poor results from the above cranking test may not necessarily indicate a faulty battery. If this first test reveals an excessive voltage drop during cranking, it would be wise to next perform a voltage drop test on the battery cables. This involves using your multimeter again set on DC volts. Place the red lead on the negative battery terminal with black lead connected to the ground cable bolt on the engine.
Disable the ignition and crank the starter motor. During cranking, the multimeter will display a voltage. If it reads 0.15 volt or less, this is an indication of decent low resistance in the ground cable. If the meter reads 0.16 volt or more, this indicates resistance in the cable or the connection. This same volt drop test should also be performed on the positive battery cable between the battery and the connection on the starter motor.
Often, even brand new inexpensive battery cables can cause a hot start problem that is often blamed on the battery. This is why large, multi-strand copper cable is preferred. In automotive DC starting systems, large diameter battery cables with multiple strands offer the least system resistance, especially when used with copper terminals.
Sometimes starting problems can be traced to an undersized wire feeding current to the pull-in/hold-in engagement side of the solenoid. This is especially true with high performance starter motors that demand high current flow to the solenoid. In some cases, using a high amperage relay kit to connect with the starter solenoid will prevent re-occurring hot start problems where the solenoid just clicks but will not engage the starter motor.
Many times, recurring low-voltage battery issues can be traced to the vehicle’s charging system. The first check we like to perform is a simple test that is a good indicator of charging system condition. Using a multi-meter set on DC voltage on a running engine, check the voltage at the output terminal on the alternator. Next, with the engine still running, check the voltage at the battery terminals. If the voltage reading at the battery is more than a 0.50 volt lower, this indicates the charging wire from the alternator to the battery is too small or suffers from excessive internal resistance. This is especially a important for high output charging systems.
There’s much more to this story than we can squeeze into this current events adventure, but these few tidbits should cover the major areas of batteries, starter, and charging systems that should reinforce you to pay closer attention to how these systems work and the importance of proper maintenance.
Common Vehicle Battery Terms & Definitions
- Lead-Acid Battery – This is the most common style of automotive starting battery. Lead plates are immersed in a sulfuric acid solution producing 2.1 to 2.2 volts per cell.
- Gel Type Battery – This style uses a material mixed with sulfuric acid to create a gel acid to coat the battery plates to create voltage. This technology offers an increase in performance and durability.
- Spiral-Cell Battery – This is Optima technology that wraps the cells in a spiral configuration using absorbed glass matt (AGM) that is different from gel construction. This AGM process offers improved vibration resistance which is a common cause of battery failure in lead-acid and gel type batteries.
- Lithium-Ion Battery – This dry cell technology has been used to power small devices like cell phones but is now available in automotive starting batteries. The main advantage is their extreme light weight which can be useful for race cars. The disadvantage of this design is its higher cost and that it requires a specific charger.
- Open Circuit Voltage (OCV) – this is the voltage measured at the battery terminals with no load on the battery. This is a quick and simple indicator of battery condition. Most flooded, gel, and AGM batteries will indicate maximum charge at 12.6 to 12.8 OCV.
- Cold Cranking Amps (CCA) – This is the amount of amperage the battery can deliver for 30 seconds at 0 degrees F and not fall below a 7.2 volt state of charge. Higher ratings mean the battery can deliver more amperage at cold temperatures so a battery with 750 CCA has 50 percent more cold cranking capacity than a battery rated at 500 CCA.
- Reserve Capacity (RC) – This is a specification in minutes of how long the battery can deliver a consistent 25 amps until it reaches full discharge of 10.5 volts. As an example, a full charged battery with a reserve capacity of 100 means it can deliver 25 amps of constant load for 100 minutes before it reaches 10.5 volts.
- Amp Hour (AH) – This is a similar yet different amp rating usually reserved for deep cycle batteries intended for continuous use such as powering an electric trolling motor for a boat. Most automotive batteries are rated using Reserve Capacity. Amp Hour is the maximum amount of amperage the battery can deliver for one hour at 80 degrees F before reaching full discharge at 10.5 volts. For example, a 55 AH rating would mean this battery could deliver 55 amps continuously for one hour from a full charge until it reached 10.5 volts.
3 Stages of Battery Charging Rate
Modern “smart” battery chargers will automatically shift between Stage 1, 2, and 3 modes.
- Bulk Charge (1st Stage) – This is a relatively safe high amperage charge rate that continues until the battery achieves 70 to 80 percent of max charged voltage.
- Absorption Charge (2nd Stage) – At this stage, voltage remains constant and current (amperage) is tapered down—here is where maximum voltage is achieved—voltage used in this process is usually between 14.2 and 14.7 volts
- Float Charge (3rd Stage) – This is usually a maintenance charging point with very low amperage that maintains peak voltage. This is the area where “trickle” chargers operate, using a very low (1 to 3 amp) current flow.
Common Domestic Vehicle Battery Groups
|24F||Terminals opposite 24|
|27||Slightly longer than 24|
|34||Slightly shorter than 24|
|34/78||Combination top & side terminal|
Lead-Acid Battery State of Charge
|State of Charge||Voltage|
|100%||12.6 – 12.7 Vdc|